Method and apparatus for reducing audio noise in a switching regulator
First Claim
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1. An apparatus, comprising:
- means for switching a power switch coupled to an energy transfer element of a power supply to regulate energy delivered to an output of the power supply;
means for selecting one of a plurality of states in response to the output of the power supply, each one of the plurality of states having an associated current limit value; and
means for limiting a current through the power switch in response to the associated current limit value of the selected one of the plurality of states.
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Abstract
A switching regulator utilizing on/off control that reduces audio noise at light loads by adjusting the current limit of the switching regulator. In one embodiment, a switching regulator includes a state machine that adjusts the current limit of the switching regulator based on a pattern of feedback signal values from the output of the power supply for a preceding N cycles of the drive signal. The state machine adjusts the current limit lower at light loads such that cycles are not skipped to reduce the operating frequency of the switching regulator into the audio frequency range until the flux density through the transformer is sufficiently low to reduce the generation of audio noise.
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Citations
8 Claims
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1. An apparatus, comprising:
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means for switching a power switch coupled to an energy transfer element of a power supply to regulate energy delivered to an output of the power supply; means for selecting one of a plurality of states in response to the output of the power supply, each one of the plurality of states having an associated current limit value; and means for limiting a current through the power switch in response to the associated current limit value of the selected one of the plurality of states. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification